The combustion system of a gas turbine is designed to contain the hot gasses and flame produced during the combustion process and to provide an efficient channel to transport the hot gas to the turbine section of the engine. An industrial gas turbine engine commonly has several individual combustion device assemblies arranged in a circular array about the engine shaft. A respective circular array of transition ducts, also known as transition pieces, connects the outflow of each combustor to the turbine inlet. Each transition piece may be a tubular or other appropriately shaped structure that channels the combustion gas between a combustion chamber and the first row or stage of stationary vanes or nozzles of the turbine section.
The interface between the combustion system and the turbine section occurs between an exit frame on the downstream end of each transition piece and the inlet of the turbine. Each exit frame mates with a first stage vane retaining ring or element. Upper and lower seals are provided on each exit frame to seal against respective radially outer and inner retainer elements of the first stage vanes to minimize leakage between the transition ducts and the nozzles. Side seals between each pair of adjacent exit frames minimize leakage between the exit frames. The effectiveness and reliability of both types of seals are important to achieving engine efficiency and performance goals.